1. Field of the Invention
The present invention relates to a method and an apparatus for supplying coolant in the grinding machine, while a grinding machine grinds, for grinding a workpiece by rotating a grinding wheel, and more particularly to the method and the apparatus for supplying the coolant while the grinding machine performs a creep feed grinding.
2. Description of the Related Art
In the grinding machine, a main spindle is rotated for grinding a workpiece with a grinding wheel under the condition that the grinding wheel is mounted on the main spindle movable relative to the workpiece. A coolant supply apparatus for supplying coolant (cutting fluid, grinding fluid, and the like) is provided in the grinding machine.
The coolant supply apparatus injects the coolant for cooling a grinding point at which the grinding wheel grinds the workpiece, and the coolant cools down the vicinity of the grinding point to thereby prevent a heat generation while the grinding machine grinds.
It is ideal that the coolant is injected in a tangential direction at the grinding point. However, unlike another tool in other machine tools, a diameter of the grinding wheel for grinding the workpiece is gradually decreased by wearing and dressing of the grinding wheel as the working for grinding the workpiece is advanced.
Accordingly, when a nozzle is mounted on a cover of a grinding wheel and the coolant for cooling the grinding point is injected in a direction of a tangential line of the grinding wheel as in a surface grinding machine, the coolant does not come to impinge against the grinding wheel as the diameter of the grinding wheel is gradually decreased.
Accordingly, there is a conventional technical approach that a nozzle is provided in advance at a predetermined position in a direction slightly slanted relative to the tangential line and the coolant is injected by the nozzle to cool only the vicinity of the grinding point.
Also, in order to prevent the loading chips on the grinding wheel, it is preferable that the coolant for cleaning is injected on a periphery of the grinding wheel. Therefore, there is also a technical approach that the coolant is injected onto a periphery at an intermediate portion between the grinding point and the cleaning position of the grinding wheel so that a cooling operation of the grinding point and a cleaning operation of the grinding wheel may be simultaneously performed by a single nozzle.
By the way, in order to stably grind, it is one of the important factors to always sufficiently supply the coolant at least to the grinding point without failure while the grinding wheel grinds.
While the grinding machine performs the creep feed grinding, a cutting amount of the grinding wheel to the workpiece is increased and the grinding wheel is moved at a low speed to grind a profile of the workpiece, and the like. In particular, in the case in which the creep feed grinding is carried out, in comparison with a traverse grinding or the like it is important to sufficiently supply the coolant without failure while the grinding machine grinds.
However, in case of the above-described prior art for cooling down only the vicinity of the grinding point, since it is impossible to prevent the loading chips on the grinding wheel, there is a fear that it comes to be difficult to perform the creep feed grinding. Namely, a grinding burn occurs on a surface, to be ground, of the workpiece and a grinding force is increased, disadvantageously.
Also in case of the above-described prior art for simultaneously performing the cooling operation of the grinding point and the cleaning operation of the grinding wheel with the single nozzle, there is a tendency that the cooling of the grinding point with the coolant gets to be insufficient. It is preferable that the coolant for cleaning is injected in a direction (i.e., normal line direction) perpendicular to the periphery (grinding circumferential surface) of the grinding wheel.
However, in case of the above-described prior art, there is a fear that an injecting direction of the coolant for cleaning is remarkably shifted from the normal line relative to the periphery of the grinding wheel and as a result a cleaning effect of the coolant gets to be degraded. Namely, also in this prior art, it is impossible to prevent the grinding burn and the increasing of the grinding force.
In another piece of the prior art, a nozzle is provided on a tip end of an arm of a robot fixed to a machine body and the arm is moved in a desired direction to supply the coolant. However, in this case, a movable range of the arm is restricted. For this reason, depending upon the relationship a shape of the workpiece to the grinding point positioned between the grinding wheel and the workpiece, the arm cannot reach the vicinity of the grinding point thereby to be unable to inject the coolant without failure.
Thus, if the sufficient amount of coolant were not supplied to the periphery of the grinding wheel and the grinding point, the grinding comes to be instable and the damage of the grinding wheel occurs and it becomes to be difficult to favorably grind the workpiece.
In order to overcome the above-noted defects, an object of the present invention is to provide a method and an apparatus for supplying coolant in a grinding machine in which, even if a diameter of a grinding wheel of the grinding machine is changed, the coolant is always injected along a tangential line of the grinding wheel to a grinding point at which the grinding wheel grinds a workpiece and is always injected, substantially in a direction perpendicular to a periphery of the grinding wheel, to the periphery away from the grinding point to thereby make it possible to continuously and stably grind.
Another object of the present invention is to provide a method and an apparatus for supplying coolant in a grinding machine in which, even if the diameter of the grinding wheel of the grinding machine is changed, the coolant is injected to the grinding point along the tangential line on both sides of the grinding wheel to thereby make it possible to continuously and stably grind.
In order to attain these and other objects, according to the present invention, there is provided a method for supplying coolant in a grinding machine, while the grinding machine grinds, which grinds a workpiece by rotating a grinding wheel mounted on a main spindle and by relatively moving the workpiece and the grinding wheel along at least three mutually transverse axes including a direction parallel with an axis of the main spindle, the method comprising the following steps of: mounting on a moving member at least one first nozzle, for cooling a grinding point at which the grinding wheel grinds the workpiece, and at least one second nozzle for cleaning a periphery of the grinding wheel; and moving the moving member in a direction substantially identical with a first normal line, relative to the grinding wheel, which is positioned at a first predetermined angle away from a reference straight line passing through the grinding point and being perpendicular to the axis of the main spindle, whereby the first nozzle injects the coolant with an injecting outlet port directed in a direction substantially identical with a tangential line, of the grinding wheel, passing through the grinding point, and the second nozzle injects the coolant with an injecting outlet port directed in a direction substantially identical with a normal line relative to the grinding wheel.
It is preferable that the moving member is movable in correspondence with a changing diameter of the grinding wheel, and while the diameter of the grinding wheel is changing, the injecting outlet port of the first nozzle is always directed in the direction substantially identical with the tangential line, of the grinding wheel, passing through the grinding point, and the injecting outlet port of the second nozzle is always directed in the direction substantially identical with the normal line relative to the grinding wheel.
Preferably, the moving member is movable in a direction parallel with the axis of the main spindle. The moving member swivels round the axis of the main spindle.
It is preferable that the first nozzle and the second nozzle are mounted on a single supporting member which is detachably mounted on the moving member.
Preferably, the supporting member is possible to be changed for another supporting member, at least one first nozzle and at least one second nozzle are respectively mounted on the last-mentioned other supporting member at counter positions to the mounting positions of the first nozzle and the second nozzle on the first-mentioned supporting member, and the other supporting member is detachably mounted on the moving member.
Also, it is preferable that, after the moving member is operatively swivelled round the axis of the main spindle so that the moving member is moved to a position of a second normal line, relative to the grinding wheel, which is opposite to the position of the first normal line relative to the reference straight line and is positioned at a second predetermined angle away from the reference straight line, the moving member is moved in a direction substantially identical with the second normal line, whereby the first nozzle in the counter position injects the coolant with an injecting outlet port directed in a direction substantially identical with a tangential line, of the grinding wheel, passing through the grinding point, and the second nozzle in the counter position injects the coolant with an injecting outlet port directed in a direction substantially identical with a normal line relative to the grinding wheel.
Preferably, the first predetermined angle is selected from a range of 15 to 50 degrees.
It is preferable that the coolant having a. predetermined pressure at a predetermined flow rate is supplied to the first nozzle for cooling the grinding point, and the coolant having a higher pressure than the predetermined pressure is supplied for cleaning to the second nozzle at a smaller flow rate than the predetermined flow rate.
It is preferable that the moving member makes a motion for always maintaining the same posture along a predetermined plain including the axis of the main spindle.
Preferably, the grinding machine comprises a dresser supporting member which rotatably supports at least one dresser for dressing the grinding wheel, the dresser supporting member is relatively movable to the main spindle in at least one direction perpendicular to the axis of the main spindle, wherein the grinding machine is able to grind with continuous dressing in which an operation of dressing the grinding wheel with the dresser and an operation of grinding the workpiece with the grinding wheel are simultaneously performed, wherein the coolant is injected in the direction substantially identical with the tangential line while the grinding machine grinds with continuous dressing, and the coolant is injected in the direction substantially identical with the normal line while the grinding machine grinds with continuous dressing.
In order to attain the above described objects, according to the present invention, there is provided an apparatus for supplying coolant in a grinding machine which grinds a workpiece by rotating a grinding wheel mounted on a main spindle and by relatively moving the workpiece and the grinding wheel along at least three mutually transverse axes including a direction parallel with an axis of the main spindle, the apparatus comprising: a moving member provided on a spindle head for rotatably supporting the main spindle, the moving member being movable in a plain perpendicular to at least the axis of the main spindle relative to the grinding wheel; at least one first nozzle provided on the moving member with an injecting outlet port directed in a direction substantially identical with a tangential line, of the grinding wheel, passing through a grinding point, for cooling the grinding point at which the grinding wheel grinds the workpiece; at least one second nozzle provided on the moving member with an injecting outlet port directed in a direction substantially identical with a normal line relative to the grinding wheel, for cleaning a periphery of the grinding wheel; and a nozzle moving controller for controlling the movement of the moving member in a direction substantially identical with a first normal line, relative to the grinding wheel, which is positioned at a first predetermined angle away from a reference straight line passing through the grinding point, the reference straight line being perpendicular to the axis of the main spindle.
Preferably, a nozzle supporting device having the moving member is mounted on the spindle head, and the nozzle supporting device has a mechanism for moving the moving member in a direction parallel with the axis of the main spindle. The mechanism for moving the moving member in a direction parallel with the axis of the main spindle comprises an arm swinging mechanism and a parallel link mechanism, and the moving member makes a motion for always maintaining the same posture along a predetermined plain including the axis of the main spindle.
It is preferable that a swiveling sleeve is fitted around the spindle head to be able to swivel round the main spindle so as to center the axis of the main spindle, and a nozzle supporting device having the moving member is mounted on the swiveling sleeve, wherein, when a driving motor is driven so that the swiveling sleeve makes a swiveling motion, the moving member is swivelled round the main spindle so as to center the axis of the main spindle.
In another embodiment, there is provided an apparatus for supplying coolant in a grinding machine which grinds a workpiece by rotating a grinding wheel mounted on a main spindle and by relatively moving the workpiece and the grinding wheel along at least three mutually transverse axes including a direction parallel with an axis of the main spindle, a dresser supporting member for rotatably supporting at least one dresser for dressing the grinding wheel being moved relative to the main spindle in at least one direction perpendicular to the axis of the main spindle, the apparatus comprising: at least one cooling nozzle provided for cooling a grinding point at which the grinding wheel grinds the workpiece, the cooling nozzle injecting the coolant with an injecting outlet port always directed in a direction substantially identical with a tangential line, of the grinding wheel, passing through the grinding point; a moving unit for moving in an opposite direction to a moving direction of the dresser supporting member and for moving with the same moving amount as that of the dresser supporting member; and at least one auxiliary cooling nozzle for cooling the grinding point with an assistance, the auxiliary cooling nozzle being provided on the moving unit and being located at a position facing the cooling nozzle, wherein an injecting outlet port of the auxiliary cooling nozzle is always directed in the direction substantially identical with the tangential line, of the grinding wheel, passing through the grinding point, and injects the coolant to the grinding point from a substantially opposite direction to the cooling nozzle.
Preferably, the apparatus for supplying coolant further comprising a cleaning nozzle, wherein an injecting outlet port of the cleaning nozzle is always directed in the direction substantially identical with the normal line of the grinding wheel, so that the injecting outlet port of the cleaning nozzle injects the coolant to a periphery of the grinding wheel.
With the above-described structure according to the present invention, even if the diameter of the grinding wheel of the grinding machine is changed, a sufficient amount coolant is injected at least to the grinding point without failure to thereby continuously and stably grind. Namely, there is no fear of the grinding burn of the workpiece and is no fear of the increasing of the grinding force. Also, it is possible to prolong a tool life of the grinding wheel.